In summary, neurological injury continues to be a significant source of perioperative morbidity and mortality in cardiac surgical procedures. To reduce the incidence and/or severity of these complications, a better understanding of the cerebral physiology of CPB is needed. Specifically, it is important to determine how the conduct of CPB either contributes to or modifies the response of the brain to neurological insults. Our research indicates that, in the uninjured brain, nonpulsatile perfusion per se does not appear disadvantageous in terms of brain blood flow or oxygen metabolism at 27 degrees C. Conversely, pulsatile perfusion does not appear to confer any special benefits. Whether pulsatility might influence neurological outcome in the presence of an ischemic insult remains to be determined.